U.S. Pat. Nos. 3,778,114 and 3,876,261 describe outlets in which a valve segment is movable relative to a fixed discharge trough to allow lading to enter the discharge trough during unloading of the outlet. However, if the outlet is impacted in transit, occasionally the valve segment will become wedged against the housing and the outlet will be difficult or impossible to unload. Furthermore in the outlet described in these patents an unloading conduit is attached to a cylindrical end portion of the valve element, and both the unloading hose and the valve element must be rotated during unloading. In some cases the unloading hose is heavy, making rotation of the valve during unloading difficult for the operator.
In U.S. Pat. No. 3,693,839 a pneumatic outlet is disclosed in which a horizontally movable element is mounted in the upper portion of the discharge trough, and is thus less subject to becoming jammed due to impacting of the outlet. The outlet is provided with a transverse partition which divides the outlet into longitudinally spaced compartments and horizontally movable valve elements are provided in each compartment, each activated by a separate rack and pinion operator. Longitudinally extending shafts are attached to each valve operator which extend to opposite ends of the outlet where handles are attached to provide opening and closing of each valve element from either end of the outlet. However this outlet requires transversely extending shaft seals for the rack and pinion operator, which along with the rack and pinion operator makes, the outlet expensive.
In U.S. Pat. No. 3,663,066 a valve is segment shaped. However, the lading acting on the valve tends to maintain the valve in closed position, rather than assisting the operator in opening the valve.
U.S. Pat. No. 998,393; 2,789,739 and 2,919,158 are examples of eccentrically mounted valve members used in pneumatic outlets. However in these arrangements the eccentric mounting does not assist the operator in moving the valve member toward the open position.
U.S. Pat. 3,420,501 discloses a butterfly valve having a body portion and plate portions extending on opposite sides of the body portion. However since the plate portions are of equal width, the lading weight acting on the respective plate portions results in a counterbalancing effect and no reduction in operating torque necessary to open the valve is achieved. The patent states (column 4) the weight of lading tends to rotate the valve into closed rather than open position.
U.S. Pat. No. 1,949,555 discloses a gravity outlet used in a combination hopper and box car in which an unloading door is eccentrically mounted relative to its operating shaft, and in which the opposite edge of the door seats on a ledge located at the opposite side of the discharge opening. The door is connected to the operating shaft with a cam which allows the door to be displaced laterally from the ledge for lading unloading. In this arrangement the door is connected to the operating shaft outside of the discharge opening and a counter weight is attached to the operating shaft which engages an externally mounted stop when the valve member reaches the open position. However the connection between the door and the operating shaft located externally of the outlet, and the counter weight mounted externally of the outlet significantly increases the likelihood of damage to the operation of the outlet in transit. The cam mounting of the door relative to the operating shaft to move the door laterally relative to the ledge is difficult and expensive to fabricate. Furthermore if the operating shaft and/or counter weight were impacted, the door could get stuck in the closed position, preventing unloading of the car.